• Nadirsha Shahabudeen

Checks and Tests on the Modular Electrical Substation

Updated: Feb 10

The systems installed in the fabrication yard were checked in 3 stages:

• Mechanical Completion,

• Pre-commissioning

• Commissioning

The results of the checks and tests were collected in the related check sheets for future examination and reference also in the reassembly stage of the modules in the Final fabrication yard.

One advantage of modular substations was postponement of replacing malfunctioning components during testing at the final fabrication stage without delaying delivery of the substation. With the construction of the electrical substation directly in the final fabrication yard instead there was a risk of delaying delivery of the substation because a malfunctioning component, for which there is no spare part, may require several weeks to be replaced.

A. Mechanical Completion

After installation, every simple or complex component was checked for correct mechanical installation.

The “Mechanical Completion” procedure involved from 10 to 15 checks for each component, following a sequence in accordance with the list written on preprinted forms already agreed and approved by the Client. The Mechanical Completion activities including the recording of the results, signing and stamping of the forms was done together with the Client’s inspectors.

The challenge in this case was to carry out numerous checks without interfering with the installation of other components in progress and without delaying the delivery of the substation. Since checks were carried out on the initial installation of similar components (lamps, cable glands, MCT, cable trays, F&G sensors) there were fewer problems in later installation work. This was the advantage of manufacturing and installing modular substations.

B. Pre-Commissioning

Pre-commissioning activities concerned the functioning of the simple parts of the installations. For example, for the lighting system each circuit was individually subjected to a function test (switching on/off, operating time of the batteries inside the lamps, checking the numbering of the components (TAG) belonging to the same circuit, measurement of the impedance for live-neutral and liveground malfunctions). Another pre-commissioning function check was done on the F&G sensors belonging to the same loop.

All the pre-commissioning activities were carried out in accordance with sequences stated in the relative forms. Pre-commissioning activities, including the recording of the results and affixing of stamps and signatures on the forms, were carried out together with the Client’s inspectors.

C. Commissioning

Commissioning activities concerned the functioning of every complete system.

Commissioning the HVAC system was very complex because it involved measuring the correspondence of the HVAC system to the design requirements. Therefore the temperatures at various points in the substation were measured and then the equipment involved was calibrated in order to obtain a thermal and air flow balance. Commissioning the HVAC also involved the power feed MCC of the HVAC, the variable speed drives for the fans, the static switches for the heaters, the F&G system and of course also the PLC of the HVAC.

Commissioning the lighting system was done by measuring the level of illumination in numerous zones and at predetermined points of the substations and recording the values measured for comparison with those required. An advantage of the modular substation system was the possibility of being able to add or move lamps easily in the modules to even out the level of illumination.


When all the substation systems had passed the tests, they were prepared for transport. These activities are necessary only in the case of modular substations constructed in the Fabrication yard and not directly at the final installation site.

These activities were:

• Sea fastening,

• Preservation,

• Dismantling,

• Load-out

A. Sea fastening

All the equipment installed in the modular substation was anchored mechanically to the module to prevent damage due to oscillations and vibrations during transport.

The structure of the modules was also reinforced with temporary vertical and oblique braces to stiffen the structure for lifting and transport.

Modules with temporary braces

Equipment with large dimensions such as the transformers, panels and HVAC units were anchored using tape tie rods attached to the top part of the equipment and the floor of the module.

B. Preservation

After or during sea fastening all the equipment installed in the modular substation was wrapped with sheets of special material, of a type that reduces humidity, to form a closed cover.

C. Dismantling

Dismantling was very laborious because it involved the mechanical separation of the modules after first separating the flanges of the air ducts and disconnecting the electrical cables. To ensure perfect alignment of adjacent modules guiding pins were installed.

Guiding pin system

The parts of the modules that were without walls after separation were closed with temporary wood walls.

D. Loadout

Each module was loaded using cranes or special forklifts on the barge moored near the Fabrication yard and anchored for transport.

Transfer of module


Reassembly in the final fabrication yard was performed following the detailed reassembly procedures agreed with the Client.

The sequence of activities is the same as in the fabrication yard but in reverse; for the substations with a number of modules in particular:

1. Unloading of the first module onto its final plinths,

2. Removal of the temporary wall and ceiling,

3. Removal of the temporary internal braces of the module,

4. Unloading of the next module onto temporary plinths,

5. Removal of temporary walls and ceiling,

6. Positioning of the module above or next to the module already placed using the guiding pins,

7. Removal of the temporary walls and temporary braces,

8. Repeat from point 4 for the other modules.

After mechanical reassembly of all the modules the air ducts are reassembled and the cables are reconnected following the Cable Schedule.


After reassembly of the modules to form the complete substation, the procedures were followed for Mechanical Completion (only the components reassembled on site), Pre-commissioning and then Commissioning, based on the relative check sheets produced in the Fabrication yard.

The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.

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